Variation in sensitivity of response to increasing doses of the drug in different individuals can be obtained from

Quantal DRC When the response is an 'all or none' phenomenon (e.g. antiemetic drug stopping the vomiting or not), the y-axis (response axis) shows the number of person responding and X-axis shows the plasma concentration. It thus shows that how many person respond to a paicular dose of the drug. It is used to calculate ED50 and LD50. Median Effective Dose (ED50): It is the dose that will produce the desired response in half of the (50%)recipients. More is ED50, lower is the potency and vice a versa. Median Lethal Dose (LD50): It is the dose that will result in death of 50% of the animals receiving the drug. More is LD50, safer is the drug. Therapeutic Index (T.I.): It is a measure of the safety of a drug. It is calculated as a ratio of LD50 to ED50. Drugs having high T.I. are safer whereas those having low T.I. are more likely to be toxic.